Crews have sucked up 7,300 barrels of bitumen, but with million of litres already spilled, and another 2,400 litres continuing to seep into the bush each day, critics are beginning to question the steam injection process used to extract the oil in the first place.

While steam injection, or cyclical steam stimulation (CSS), is often considered more environmentally friendly than mining, some fear the method may be causing fissures in the rock, allowing bitumen to rise to the surface and pollute marshland and waterways.

Canadian Natural Resources Limited president Steve Laut told the Wall Street Journal he's confident poorly-capped, abandoned well bores are what caused the leak, allowing bitumen to flow into cracks in the rock and migrate horizontally; not weakness in the surrounding cap rock.

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Alberta Oil Spills

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Environmental organizations, on the other hand, say the high-pressure steaming has fractured capstone.

However, critics say the company is jumping to conclusions and should be investigating the matter further, especially considering the similarities between this leak and a 2009 spill the company faced in the same area which saw 5,600 litres spill into surrounding wetlands.